title: A modulator which converts activated estrogen receptor to a biologically inactive aggregated form.
abstract: The in vitro nuclear binding of rat uterine estrogen-receptor complexes has been studied. Heating cytosol from mature rat uterus at 25 C for various times in the presence of 0.15 M KCl resulted in a transient increase in nuclear binding activity, followed by irreversible loss of this activity. The molecular state of these complexes heated at 25 C in the presence of 0.15 M KCl was determined using Sephadex G-200 chromatography and sucrose density centrifugation at high ionic strength (0.4 M KCl). Gel filtration resulted in steroid-binding activity in the void volume. Sucrose density gradient analysis revealed a broad peak, ranging from approximately 5-20S. When cytosol was heated at 25 C in the presence of 10 mM molybdate to block the temperature-induced activation of receptor, nuclear binding ability was easily recovered by dialysis, while heating already activated estrogen receptor in the presence of 0.15 M KCl and 10 mM molybdate caused irreversible loss of nuclear binding ability. When cytosols prepared from immature rats (19-23 days old) were heated at 25 C in the presence of 0.15 M KCl, only a minimum loss of nuclear binding ability was shown. The radioactive peak in a high salt sucrose density gradient appeared almost exclusively in the 5S region. However, the addition of receptor-free mature uterine cytosol to estrogen-receptor complexes from immature rat uterus caused a marked loss of nuclear binding utility, with a resultant receptor aggregation, whereas rat liver cytosol had no effect on this reaction. Furthermore, heating liver glucocorticoid receptor did not cause a loss of nuclear binding ability even in the presence of receptor-free adult rat uterine cytosol. These observations suggest that there is a factor(s) in rat uterus which recognizes only activated estrogen receptor and induces receptor aggregation and a rapid loss of the nuclear binding ability of receptor in a KCl concentration- and temperature-dependent manner. Preliminary characterization indicates that this factor is macromolecular in nature and resistant to RNase and trypsin treatment, but labile at 100 C.
mesh_terms: D000818:Animals; D002467:Cell Nucleus / Q000187:drug effects / Q000378:metabolism*; D003600:Cytosol / Q000502:physiology; D004492:Edetic Acid / Q000494:pharmacology; D005260:Female; D007700:Kinetics; D046911:Macromolecular Substances; D009994:Osmolar Concentration; D011189:Potassium Chloride / Q000494:pharmacology; D051381:Rats; D011919:Rats, Inbred Strains; D011960:Receptors, Estrogen / Q000187:drug effects / Q000378:metabolism*; D012741:Sexual Maturation; D013696:Temperature; D014599:Uterus / Q000378:metabolism*
chemical_list: D046911:Macromolecular Substances; D011960:Receptors, Estrogen; D011189:Potassium Chloride; D004492:Edetic Acid